Body air spaces like the lungs, the ears, the sinuses can suffer barotrauma (pressure injury) on descending or ascending. During descending or ascending hydrostatic pressure changes. Trouble occurs if the diver fails to equalize the air space. On descending a barotrauma is called squeeze. Tissue is forced into the air space. On ascending a barotrauma is called reverse squeeze, reverse block or expansion injury. These injuries involve expanding air in the air space. Barotraumas can be prevented by following of the proper procedures for diving.
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Lung problems occur when a diver ascends while holding his breath. Since the air in his lungs was breathed at depth, the pressure is the same as the surrounding (water) pressure. When the diver ascends, the surrounding pressure decreases. When holding his breath, the air in the divers lungs expands (increasing volume) to keep the pressure equal to the surrounding pressure (Boyle's law). If no more expansion is possible because the maximum volume of the lungs is reached, the lungs get overpressurized. Lungs cannot take to much overpressure so they start to tear up. Air can enter tissue or the bloodstream. Over pressurizing can easily happen: ascending as low as one to one and a half meter with full lungs can give rise to lung injuries. Especially in shallow water, the pressure drop (resp. volume increase) per ascended meter is largest.
Another reason for lung problems is air getting trapped in a
part of the lungs due to obstruction of this part. During ascending
similar process takes place as described above. Obstruction can
occur due to: Problems due to over pressurizing lungs are: Any lung over pressurization causes rupture of alveoli and capillaries, mixing blood and air in the lungs. Often this causes the victim to cough up blood. |
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Arterial Gas Embolism, abbreviated as AGE, occurs if air escapes through ruptures in lung alveoli into the bloodstream (pulmonary capillaries). From these pulmonary capillaries the air flows to the left side of the heart through the pulmonary veins. From here the air enters the aorta and can reach any part of the body. The air forms bubbles, which tend to clog together forming larger bubbles. If these bubbles block arteries we call this embolism. The air can flow through the aortic arch to the brain. Brain tissue arteries can be blocked causing cerebral air embolism. Like decompression sickness this causes a stroke. Symptoms are confusion, dizziness, disorientation, shock, paralysis, loss of consciousness and even death. Though these symptoms are comparable to those of decompression sickness, AGE symptoms are rapid and dramatic, whereas DS symptoms are somewhat delayed. Symptoms occur during and right after surfacing.
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When the inner of the two pleura ruptures, air will flow into the pleural cavity. This is called pneumothorax A pneumothorax is in general not immediately life-threatening like an AGE. However, there is a possibility that a flap of tissue acts as a valve: on inhaling, air flows out of the lung into the pleural cavity. On exhaling however, this air does not flow back forcing the lung to collapse partially or entirely. This is called tension pneumothorax. Air accumulating on one side of the chest may result in shifting of the mediastinum, compressing the other side as well. A tension pneumothorax is life-threatening. Though uncommon (1 pneumothorax on 10.000 people) pneumothorax may occur spontaneously due to week spots (bullae or 'blebs') in the lung, causing sudden rupturing. Spontaneous pneumothorax occurs often on young people (25-35 years) and is more common by smokers. Spontaneous pneumothorax happening to a diver under water is more serious. The trapped air expands on ascending, increasing the pressure on the collapsed lung. Spontaneous pneumothorax tends to recur. Diving is therefore precluded, unless the problem is corrected by surgery. Another cause for pneumothorax is a penetrating injury of the chestwall. This is called traumatic pneumothorax. |
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A pneumothorax causes severe pain in the chest and may cause the victim to cough up frothy blood. Other symptoms are shortness of breath, increased breathing rate and awareness of 'splash', 'movement' or 'flopping' bubbling sensation in the chest. A tension pneumothorax causes severe shortage of breath. Pneumothorax is treated by aspiration of the air though a Teflon tube, which is inserted in the pleural cavity, letting the lung expand again. Small pneumothorax (spontaneous) may resolve without treatment.
In a mediastinal emphysema or pneumo mediastinum air accumulates in the mediastinum. This is the center of the chest between the lungs where the heart resides. Air may press on the heart and major arteries, interfering with circulation. Symptoms are feeling faint and feeling short of breath. However, mediastinal emphysema is far less serious than AGE or pneumothorax.
In a subcutaneous emphysema air accumulates under the skin in the neck (subcutane means 'under the skin'). Often subcutaneous emphysema results from a mediastinal emphysema, when air seeks its way out of the mediastinum. The way of least resistance is the way into the soft tissue at the base of the neck. Victims experience a fullness of the neck and a change of voice. An odd symptom may be a cracking sound when touching the skin of the neck.
A thoracic squeeze occurs when the lung volume is reduced beyond the residual volume due to increased ambient pressure. This situation may occur when a breath-hold diver dives to extreme depths. When the breath-hold diver goes down, increasing ambient pressure compresses the lungs (chest). The volume of the lungs decreases (Boyle's law). Normally this does not give rise to problems. However when extreme depths are reached, the lung volume might be reduced beyond the residual volume. This is the reason that depth record (150 m) breaking breath-hold divers have to take a breath of air when they are half way down during the descent. A thoracic squeeze may occur also when a scuba diver descends while having completely exhaled (for trimming for example). In this case a descent of a few meters is sufficient to cause a thoracic squeeze.
Compression beyond residual volume causes pulmonary capillaries to swell, causing fluid to leak into the lungs. If the compression is slight and the duration of it is short, there is little effect because only small amounts of fluid will enter the lungs. However on extending squeezes or larger compressions the fluid may enter the alveoli, interfering with the gas exchange. Such a thoracic squeeze causes shortness of breath. A thoracic squeeze might be life-threatening and needs medical attention.
Common ear problems during diving are:
If the diver fails to equalize during descending the increasing ambient hydrostatic pressure forces the eardrum to flex inwards (the air volume in the middle ear decreases). First this is experienced as an uncomfortable feeling. As the depth and the ambient pressure continue to increase, the feeling will go over in a sharp pain. Blood and fluid are forced from the surrounding tissue into the middle ear (effusion). This is called barotitis The longer the diver remains unequalized, the more fluid is forced into the middle ear. If the middle ear is full the pain diminishes (fluid is incompressible whereas air is compressible). The ear feels 'full' and hearing is affected because the fluid dampens the vibrations.
A middle ear squeeze usually heals with the proper treatment of an otolaryngologist (ear, nose and throat specialist). Permanent hearing damage may be the result due to infection if no proper medical attention is paid to the problem. Treatment usually consists of antibiotics, decongestant and, in persistent cases, steroids. Usually it takes up to six weeks for all fluid to have been reabsorbed or drained by the Eustachian tube. In rare occasions small ventilating tubes may be necessary to be placed in the eardrum to prevent fluid recurrence. Flying and diving should be avoided in case of barotitis.
If the diver with unequalized ears descends fast the possibility exists that his eardrum will rupture by the increasing hydrostatic pressure before the middle ear is filled up with fluid. This is experienced as a sharp pain followed by immediate relieve when water enters the middle ear through the rupture, instantly equalizing the ear. The diver may experience vertigo, since the relatively cold water comes into contact with the vestibular canals. When the water in the middle ear is warmed up by the body the vertigo disappears. Blood in the outer ear indicates eardrum rupture.
If a diver suspects eardrum rupture under water, best action he can take is to alert his buddy and slowly return to the surface and get medical attention. Usually a broken eardrum heals quite well. However the water in the middle ear may cause infections. Medical attention provided by an otolaryngologist may reduce the risk of permanent hearing loss due to eardrum rupture. Small ruptures heal within six weeks. Perforations that do not heal require a tympanoplasty operation: a tissue graft is placed over or under the perforation in order to repair it.
A reverse squeeze occurs during ascending if the Eustachian tube is blocked during the dive. This frequently occurs if a diver with a cold or an allergy uses a nasal decongestant. If the decongestant wears out under water the Eustachian tube may be blocked again.
Decreasing ambient hydrostatic pressure during ascent forces the eardrum to flex outward. The diver has to ascend eventually because his air supply is limited, whether he manages to equalize or not. On rare occasions a persisting reverse squeeze may lead to eardrum rupture. In some cases divers succeeded to equalize using reverse equalizing: pinching the nose while inhaling.
A lengthy and forceful Valsalva maneuver after delayed equalization may cause round window rupture. This injury may feel as blocked ears and may be experienced as reduced hearing, often accompanied by the hearing of ringing and vertigo.
The principle of this injury is rather complex: on increasing hydrostatic pressure the eardrum flexes inwards. This inward flexing is transmitted and amplified to the oval window of the cochlea by the hearing bones. The oval window flexes inwards, exerting pressure on the perilymph. This causes the round window to flex outwards.
Throughout the body cerebrospinal fluid is produced. This fluid bathes the nerves of the head and spinal cord and includes the perilymph. The fluid is continuously produced and absorbed by the venous system. During the Valsalva maneuver, pressure in the chest momentarily rises. Blood flow in the major veins to the heart is inhibited, increasing the pressure in these veins. The venous pressure temporarily increases the pressure in the cerebrospinal fluids, including the perilymph. This increase adds up to the already increased pressure transmitted from the eardrum to the perilymph. This may cause rupture of the round window.
A round window rupture is a serious injury and need medical treatment by an otolaryngologist. Failure to do so may result in reduced hearing or deafness. Treatment consists of bed rest, avoidance of exercise and loud noises. If hearing does not improve, reconstructing surgery may be necessary. The diver should not dive or fly for several months.
Swimmers ear or otitis externa is actually not pressure related. However it is one of the most common ear problems among divers (and swimmers). Swimmers ear occurs if the pH of the ear canal goes from acid to alkaline, due to exposure to water or humidity. This gives fungi and bacteria a chance. Inflammation of the outer ear is the result. Symptoms can range from a troublesome itch to complete closure of the external ear canal, swelling, fever and severe pain.
Best treatment is prevention by flushing the ear canal with one of those over-the-counter solutions (usually containing vinegar acid) for this purpose. Flushing should take place routinely after each dive (or whenever the ear gets wet). Extensive earwax should be removed by an otolaryngologist periodically. Repeated cold water exposures may lead to exostoces, bony bumps in the divers ear canal. These exostoces can trap debris in the ear canal. A diver with this condition should have his ears cleaned at least twice a year by an otolaryngologist. Sometimes a fungus infection 'hides' in the ear canal.
A severe swimmers ear needs medical treatment such as cleaning of the ears, antibiotics, placing a wick in the ear canal, eardrops, heat lamp and pain medication. The diver should avoid water in his ear, as long as the ear is not healed completely.
During a cold or due to an allergy the sinuses may get obstructed by mucus. Diving with blocked sinuses may lead to sinus squeeze on descending. The diver may or may not experience sinus squeeze as pain between the eyes, alongside the nose, over the teeth or in the cheekbones. The hydrostatic pressure acts on the air filled spaces, forcing blood and fluid from the tissue into the air spaces. This is called barosinusitis. As the sinuses are filling usually the pain seizes.
On ascending the air in the sinuses expands and forces the blood and fluid into the nasal cavity. The diver ends up with blood in the mask, a definite indication of sinus squeeze.
Usually sinus squeezes heal on their own. Medical attention is needed only in case of severe or extended pain accompanying the squeeze. Treatment by an otolaryngologist usually consists of oral antibiotics and decongestants. Sometimes relief with nasal spray and alternating hot washcloths and ice packs on the cheeks to open drainage pathways help the diver obtain relief. The physician may also recommend pain medicine.
Air in equipment should be equalized as well. Common problem is mask squeeze, which may occur on rapid descents when the diver neglects to equalize the air in the mask (by blowing air through the nose into the mask). The increasing hydrostatic pressure makes the tissue in the unequalized mask swell. Due to the swelling capillaries round the eyes and cheeks may be damaged, bruising the skin. Sometimes surface capillaries on the eye are damaged as well.
Mask squeeze may look dramatic. However, it usually heals without any problem. Sometimes the diver is not aware of mask squeeze, until he looks in the mirror.
Sometimes an unequalized dry suit (or rarely air trapped in a wet suit) may pinch and bruise the skin on descending. If the diver continues to descend, disregarding the pinching, the dry suit squeeze can raise welts and cause injuries.
On rare occasions air trapped under tooth fillings have caused problems. In other rare occasions gas accumulated in the intestines during the dive may expand on ascending, causing problems. In principle any place in the body where gas or air is trapped may give rise to barotrauma.
In most of the fatal scuba diving accidents drowning appears to be the cause. Drowning occurs when the diver is unable to breathe air being in or under water. This may be caused by incidents like running out of air, panicking, exhaustion at the surface, loss of consciousness due to diabetes, epilepsy, hypothermia, and so on. We speak of drowning if the victim dies. We speak of near drowning if the victim doesn't (at least not immediately).
In a drowning or near drowning accident the victim may or may not inhale water. In 15 percent of the accidents the larynx is closed, probably as a reflex to immersion. In this situation the victim suffocates. If on the other hand, respiration is reestablished before any irreversible circulatory or neurological injury takes place, this leads to a speedy recovery without many problems.
In about 85 percent of the accidents water is inhaled. This causes lung injuries that persist long after the victim has been taken from the water. Water dissolves surfactant, which leads to collapsing of the alveoli. This leads to hypoxemia (low blood Oxygen levels), which is followed by hypoxia (low tissue Oxygen levels). Even if a victim happens to recover from a near drowning accident, medical care is absolutely necessary. Due to the damage of the surfactant alveoli and bronchioles may collapse and fluid may slowly fill up the lungs, eventually (after hours or even days) leading to hypoxia which is frequently fatal. This process is called secondary drowning.